Is there a shortcut to draw a 45 or 90 degree angle from a drawn line on an angle?

I'm not sure if that's scriptable, it depends, if it straight lines...maybe....can you post some screen shots?

wells,

As I (mis)understand it, you may (Smart Guides are your friends):

1) Add an Anchor Point (if needed) wto the drawn line where you wish to have the angle;

Depending on whether the drawn line is straight or curved;

2a) For a straight drawn line, just copy the drawn line;

2b) For a curved drawn line, Direct Select the Anchor Point from 1) so you can see the Handles (deselect first), then switch to the Line Tool and ClickDrag from one of the Handles to the Anchor Point (Smart Guides say handle and anchor when you are there);

3) Select the line from 2), switch to the Rotate Tool, click on the Anchor Point to make it centre of rotation (Smart Guides say anchor when you are there), and drag somewhere on the line to rotate it by the 45 or 90 degrees (Smart Guides say on and origin 45/90 degrees when you are there);

4) Use the rotated line from 3) as the basis for the angle, either as part of it or as a guide for creating it (especially for a curved path starting at the angle).

If you just wish to have an identical path rotated by 45/90 degrees, you may use 2a) whether straight or curved and skip 4).